This invention relates to a method of forming a coating on a polyolefin substrate.
Polyolefin resins such as polyethylene, polypropylene and the like have been widely used for protective and anticorrosive purposes of iron and other metallic substrates owing to their low water-absorption and low moisture-permeability characteristics and their high anticorrosive properties. However, their adhesion to the same or different resins is very poor and thus repairing or finishing imperfections on the polyolefin surfaces are possible only with unsatisfactory results. Such imperfections may be repaired, for example, by applying a polyolefin sheet onto the polyolefin surface and fusing together. This method is not satisfactory because the resulting coating film tends to peel off from the applied surface due to the difference in thermal expansion coefficient between the resin and metals.
Various primer coating compositions are known for improving adhesion characteristics of finish coats to be applied on polyolefin substrates. However, none of known primer compositions can achieve satisfactory results.
Thus, there is a long-felt but unfilled need for a primer coating composition which can greatly improve the bonding strength of a coating film to polyolefin substrates.